Image recording apparatuses that record color images onto recording media using an inkjet system by moving an ejection part relative to the recording media have conventionally been used, the ejection part having a plurality of nozzles arranged and each ejecting fine droplets of ink. Color images are recorded by forming ink dots at each pixel position on a recording medium on the basis of halftone image data that is generated through halftone processing. Such image recording apparatuses, however, may cause poor color reproduction due to colors becoming dull or cockling (a phenomenon where the surface of a recording medium becomes rippled) as a result of ink dots of multiple colors greatly overlapping at each pixel position on a recording medium.
Japanese Patent Application Laid-Open Nos. 11-010918 (Document 1) and 2000-354172 (Document 2) disclose methods for reducing graininess of images by recording only an ink dot of a single color at each pixel position. In Japanese Patent Application Laid-Open No. 2010-241052 (Document 3), halftone processing is performed on a color image on the basis of an evaluation index that indicates the degree of dispersion of overlapping of dots on a recording medium. This suppresses overlapping of dots and accordingly reduces graininess of the image.
Documents 1 and 2 can suppress dulling of color due to overlapping of multiple color dots, but it is difficult to represent dark mixed colors. In addition, if ink landing positions shift from their desired positions and change the overlapping state of multiple color dots, the influence of that change is greatly reflected in coloration. Document 3 can also suppress dulling of color due to overlapping of multiple color dots, but it gives no consideration to the total amount of ink applied to each pixel position. It is thus difficult to appropriately suppress cockling.
With these image recording apparatuses, ink of a specific color component may have a lower density than those of inks of the other color components, i.e., the ink of a specific color component may have a lower content of coloring material such as pigment than the inks of the other color components. In this case, if the amount of ink applied is restricted in order to suppress overlapping of dots, the color reproduction of the specific color component may deteriorate and it may not be possible to represent the desired hue when a region where the specific color component has a high tone value is written.